Document MMyzwR08gpGd0DdNYQNXgqrvV

686 CHAPTER 39 1946 Guide Table 6. Properties of Monofloorotrichlorombthane (F-H) Temp. F La per Sq Ik. Liquid Vapor Specific Enthalpy and Entropy Taken From --40 F Specific Enthalpy Entropy 25 F Superheat 50 F Superheat liquid Vapor liquid Vapor Sp. En. Entropy Sp. En. Entropy it 0 2.59 0.01020 13.700 7.81 90.4 0.0178 0.1975 93.9 0.2049 97.4 0.2120 5 2.96 0.01024 12.100 8.81 91.2 0.0200 0.1974 94.7 0.2047 98.2 0.2117 10 3.38 0.01028 10.700 9.82 92.0 0.0222 0.1973 95.5 0.2045 99.0 0.2114 I 15 .3.85 0.01032 9.530 10.80 92.8 0.0243 0.1971 96.3 0.2043 99.8 0.2111 20 4.36 0.01036 8.490 11.90 93.7 0.0264 0.1970 97.2 0.2041 100:7 0.2109 25 4.94 0.01040 7.580 12.90 94.5 0.0286 0.1969 98.0 0.2039 101.5 0.2107 30 5.57 0.01045 6.770 13.90 95.3 0.0307 0.1969 98.8 0.2038 102.3 0.2105 35 6.27 0.01049 6.080 14.90 96.1 0.0328 0.1968 99.6 0.2037 103.1 0.2103 40 7.03 0.01053 5.460 16.00 96.8 0.0349 0.1968 100.3 0.2036 103.8 0.2101 45 7.88 0.01057 4.920 17.00 97.6 0.0370 0.1967 101.1 0.2035 104.6 0.2099 50 8.79 0.01062 4.440 18.10 98.4 0.0391 0.1967 101.9 0.2034 105.4 0.2098 55 9.80 0.01066 4.020 19.10 99.2 0.0412 0.1967 102.7 0.2033 106.2 0.2097 60 10.90 0.01071 3.640 20.20 100.0 0.0432 0.1967 103.5 0.2033 107.0 0.2096 65 12.10 0.01076 3.300 21.30 100.8 0.0453 0.1967 104.3 0.2032 107.8 0.2094 70 13.40 0.01081 3.000 22.40 101.5 0.0473 0.1967 105.0 0.2032 108.5 0.2093 75 14.80 0.01086 2.740 23.50 102.2 0.0493 0.1967 105.7 0.2031 109.2 0.2092 80 85 90 95 100 - 105 16.30 0.01091 17.90 0.01096 19.70 0.01101 21.60 0.01106 23.60 0.01111 25.90 0.01116 2.500 2.280 2.090 1.918 1.761 1.620 24.50 25.60 26.70 27.80 28.90 30.10 102.9 0.0513 0.1966 106.4 0.2030 109.9 0.2090 103.6 0.0533 0.1966 107.1 0.2029 110.6 0.2089 104.4 0.0553 0.1966 107.9 0.2028 111.4 0.2088 105.1 0.0573 0.1966 108.6 0.2028 112.1 0.2087 105.7 0.0593 0.1965 109.2 0.2027 112.7 0.2085 106.4 0.0613 0.1965 109.9 0.2026 113.4 0.2084 Note: Sp. En. -- Specific Enthalpy. Table 7. Properties of Water 8at. Temp. F Abs. Lb FEB Sq In. liquid Vapor Specific Enthalpy and Entropy Taken From +32 F Specific Enthalpy Entropy 50 F Superheat 100 F Superheat liquid Vapor liquid Vapor Sp. En. Entropy Sp. F.n, .Entropy 32 0.0887 q.01602 3296.0 0.00 1073.0 0.0000 2.1826 1096.9 2.2277 1120.8 2.2688 35 0.1000 6.01602 2941.0 3.02 1074.4 0.0062 2.1724 1098.3 2.2172 1122.2 2.2581 40 0.1217 0.01602 2441.0 8.05 1076.8 0.0163 2.1555 1100.6 2.2000 1124.5 2.2406 45 0.1475 0.01602 2034.0 13.07 1079.2 0.0262 2.1390 1102.9 2.1832 1126.7 2.2234 SO 0.1780 0.01602 1702.0 18.08 1081.5 0.0361 2.1230 1105.2 2.1667 1129.0 2.2066 55 0.2140 0.01603 1430.0 23.08 1083.9 0.0459 2.1073 1107.5 2.1506 1131.3 2.1902 60 0.2561 0.01603 1206.0 28.08 1086.2 0.0556 2.0920 1109.8 2.1349 1133.5 2.1742 65 0.3054 0.01604 1021.0 33.08 1088.6 0.0652 2.0771 1112.2 2.1196 1135.8 2.1585 70 0.3628 0.01605 868.0 38.07 1090.9 0.0746 2.0625 1114.5 2.1046 1138.1 2.1432 75 0.4295 0.01606 740.0 43.06 1093.2 0.0840 2.0483 1116.7 2.0900 1140.3 2.1283 80 85 90 95 100 105- 0.507 0.596 0.698 0.815 0.949 1.101 0.01607 0.01609 0.01610 0.01612 0.01613 0.01615 632.9 543.3 467.9 404.2 350.3 304.4 48.05 1095.5 0.0933 2.0344 1119.0 2.0758 1142.5 2.1138 53.04 1097.8 0.1025 2.0208 1121.2 2.0619 1144.7 2.0996 58.03 1100.0 0.1116 2.0075 1123.4 2.0483 1146.8 2.0857 63.01 1102.3 0.1206 1.9946 1125.6 2.0350 1148.9 2.0721 68.00 1104.6 0.1296 1.9819 1127.9 2.0220 1151.1 2.0588 72.98 1106.8 0.1384 1.9695 1130.2 2.0093 1153.2 2.0458 Noth: Sp. En. = Specific Enthalpy. Refrigeration_____________ ______________ 687 ' Consider, for example, F-12 with a quality (the per cent in vapor form) of 30 per cent; the specific enthalpy of this material would be equal to: hm = kt + 0.30 (feT - fci) where hm -- specific enthalpy of the mixture. hi = specific enthalpy of the liquid. A = specific enthalpy of the saturated vapor. (2) Values of h\ and hv are obtained from Table 1 for the actual pressure of the mixture. By a reversal of this same procedure the tabular data can be used to determine .the state of a mixture leaving an expansion valve. Consider a valve to which saturated liquid at pressure ps is admitted and a mixture of saturated liquid and vapor at pressure pi is discharged. The quality of the material at discharge is then determined by making use of the fact that the expansion process is completly irreversible, is a throttling process, and hence occurs without change in enthalpy. Thus the enthalpy of the mixture, hm, is equal to the enthalpy of the saturated liquid at the entrance state, his, and can therefore be read from the table. Thus, Ais = hm = Ayd -- (1 -- *) (Ayd -- Aid) or, * = (Ara - Aid) -e (Ayd -- Aid) where his = specific enthalpy of saturated liquid at entrance to expansion valve. Am = specific enthalpy of mixture. Ayd = specific enthalpy of saturated vapor at discharge. Aid = specific enthalpy of liquid at discharge. x = proportion of liquid in the mixture. (3) (4) The refrigerant cycle is the series of state changes which occur in the conditioning processes needed to restore the refrigerant to a condition in which it will possess the ability to extract heat from the space to be cooled. For all compression-type systems the cycle consists of four processes: heat gain in the evaporator; pressure rise in the compressor; heat loss in the condenser; pressure loss in the expansion valve. The compression process is accomplished at the expense of energy added to the compressor in the form of shaft work and the expansion process could be carried out, if the economics of the system would permit, in an expanding engine with consequent release of energy as shaft work. In ordinary systems, however, the additional first cost and maintenance costs of an expanding engine so greatly exceed the advantage resulting from the work realized that such engines are not used and the pressure reduction is allowed to occur irreversibly in an expansion valve. Basic ally, then, a refrigeration cycle consists of two heat transfer processes and two pressure change processes, no work entering into the heat transfer processes and--in the simple cycle--no heat transfer occurring during the pressurfe-change processes. Simple Refrigeration Cycles The most common and least complicated type of refrigeration cycle is shown in Fig. 1 and is called the simple saturation cycle. For this system saturated vapor flows without gain or loss of heat from the